The present invention relates to developer recovery devices, which recover and accommodate developer that is residual on an image carrier, and to image forming apparatuses including the same.
Electrophotographic apparatuses are an example of this type of image forming apparatus. In image forming apparatuses of this type, an electrostatic latent image is formed on an image carrier, then the electrostatic latent image on the image carrier is developed using toner to form a toner image on the image carrier, the toner image is transferred from the image carrier to a recording paper, then the recording paper is subjected to heat and pressure to fix the toner image onto the recording paper.
Picture quality is reduced in this image forming apparatus if residual toner on the image carrier is left as it is, and therefore the apparatus may have a configuration in which residual toner on the image carrier is removed and recovered in a recovery container. Furthermore, it is configured such that when the recovery container becomes full of toner, this is detected and reported so as to advise replacement of the recovery container.
For example, in the developer recovery devices described in JP 2006-235382A (hereinafter referred to as Patent Document 1) and JP H8-129329A (hereinafter referred to as Patent Document 2), residual toner on a photosensitive drum or transfer belt is removed, and the removed toner is transported to a recovery container by a transport screw such that the removed toner is recovered in the recovery container.
An agitator member is provided in the recovery container and the toner is agitated by the agitator member. Furthermore, a torque limiter is provided at a shaft that transmits rotational force to the agitator member in the developer recovery device. In this developer recovery device, when the recovery container becomes full of toner and an overload is exerted on the agitator member such that the agitator member becomes unable to rotate, the torque limiter becomes disjoined. When the torque limiter becomes disjoined, this is detected and a full state (recovery container full state) is determined indicating that the recovery container has become full of toner.
In this regard, in Patent Documents 1 and 2, cams are provided in the torque limiter, and these cams engage with each other and are arranged on two shafts that transmit rotational force to the agitator member, and when an overload is exerted on the agitator member and the agitator member stops such that the rotation of one of the shafts stops, the cams slip and the shaft connection is disjoined. With this technique, the disjoining of the shaft connection is detected, thereby determining that the recovery container is in a full state.
With a torque limiter such as this, sometimes the engagement state between the cams becomes unstable when the load on the agitator member increases close to an overload, and the disjoined state of the shaft connection also becomes unstable. Furthermore, in Patent Document 1, the recovery container is determined to be in a full state immediately upon detection of disjoining of the shaft connection, and therefore sometimes this determination is made even though the recovery container is not sufficiently full, which is a false determination.
Accordingly, the present invention has been devised in consideration of the conventional problems described above, and it is an object thereof to provide a developer recovery device that is capable of accurately determining whether or not the recovery container is full of toner, and an image forming apparatus including the same.